This invention relates to composites of boronic acid or derivatives thereof, such as boronates, and an organic or organometallic moiety including a functional group, which when cross-linked can be used as individual layers in multi-layer opto-electronic devices, such as light emitting devices.
Many organic or polymeric optic, electronic and optoelctronic devices, such as light-emitting diodes (LEDs), field-effect transistors (FETs), solar cells, optical waveguides, etc., require high quality organic multi-layered configurations to optimise their performance.1-3 
In the fabrication of organic or polymeric light emitting devices it is advantageous to incorporate multi-layered structured materials with special functions into different location within the device. For instance, organic or polymer light-emitting diodes (LEDs) with a stack of hole-transporting, electron-transporting, and light-emitting layers exhibit enhanced device efficiency, higher brightness, and better stability. Solvent-based or wet-processing techniques such as reel-to-reel printing, screen-printing or spin-coating are important fabrication techniques that could significantly reduce fabrication costs of organic/polymer devices. However, the fabrication of multi-layer device structure is often difficult with wet-processing techniques. One typical problem of making multi-layered structures using solutions is the fact that the solvent used for each successive layer can lead to swelling or dissolution of underlying layers.
In addition, in the case of some polymeric materials, it has been found when they are used in applications such as light-emitting diodes aggregation and excimer formation can occur which can cause poor optical stability in the fabricated devices.4 For example, upon heating, or on passage of an electrical current through a polyfluorene based polymer, the formation of a long wavelength emission is frequently observed in the region 500-600 nm which can cause a drastic drop in the emission efficiency.5 
(A) Multi-layer devices, are currently being fabricated using the following methods:
(i) For low molecular weight organic materials, vacuum deposition is usually used for making a multi-layered device structure.
(ii) Since a multi-layered device structure is advantageous in highly efficient polymer based devices, much research effort has been devoted to this area. Researchers have developed different strategies to fabricate multi-layered PLED structures using 1) polymer materials with very different solubilities for the different layers in a multi-layered structure, 2) plastic lamination processes or cross-linkable polymer layers, as well as 3) chemical vapor deposition to avoid the use of solvents. Bernius et al.6 reported the use of fluorene triphenylamine copolymers with carboxylic acid substituents for the hole-transport layer, as these are soluble in polar solvents like DMF, but practically insoluble in aromatic hydrocarbons such as toluene and xylene. An electron-transport and emitting fluorene polymer layer was then spin-coated on top of this layer using a xylene solution. A double layer structure with sharp polymer-polymer interface was successfully produced using this method. Hay et al. have developed a new series of arylamine-based hole-transport polymer7,8 that can only be dissolved in some organic solvents such as chloroform, for use in the fabrication of double layer PLEDs. By using electron transporting polymers that are soluble in toluene, double layered polymer blue light emitting devices have been successfully fabricated 9. Yang and his co-workers10 recently reported a low temperature lamination method using a template activated surface process' to fabricate high performance double layer blue and red-emitting PLEDs at a temperatures much lower than the Tg of the polymers used in their devices. The discovery of cross-linkable oligo- and poly(dialkylfluorene)s series11-13 certainly opened the door for multi-layer PLED fabrication using solution processable and thermally cross-linkable polymeric or oligomeric materials. As an alternative approach for making multi-layered polymer devices, Murata14 recently reported a two-layered polymer light emitting device prepared by a vapor deposition polymerization process, which has the advantage of using a solvent-free fabrication environment to produce a good thin film with consistency in uniformity, and minimum contamination. Unfortunately the fabrication costs associated with this process are a problem. In addition it the vapor phase polycondensation reaction used in this process may be difficult to apply to other polymer systems.
(B) In terms of the problems associated with aggregation and excimer formation, several approaches16-18 have been proposed to stabilise the optical properties of polymers used in light-emitting materials. These include:
(i) Incorporation of bulky substituents into the polymer backbone or at the chain ends to enlarge the intermolecular distance.
(ii) Copolymerization with other monomers to hamper chain alignment.
(iii) Introduction of spiro-structures to decrease the crystallization tendency.
(iv) Thermal-crosslinking of precursor oligomers via styryl chain end groups to form amorphous networks.
Although the vacuum deposition is a very good technique for the fabrication of multi-layered device structure, it is limited to low molecular weight organic materials and because of the use of a high vacuum system, the production costs will be higher than using solvent-based wet processing techniques. Another possible disadvantage is that crystallization of the organic thin films may occur upon heating or operation, which could cause device failure.
The use of crosslinkable polymeric materials meanwhile through spin-coating, solution-casting, or dip-coating requires the attachment of crosslinkable functionalities to the polymers. This can complicate the synthetic procedure and needs to be optimised in terms of crosslink content and crosslinking conditions. In addition, in many cases thermal or photo initiators are necessary for the crosslinking reactions to occur. These initiators can give rise to very reactive radicals, which have the potential of altering the materials' chemical structure, which can result in defects, which may be detrimental to the device's performance and lifetime. In addition the presence of initiator residues can contaminate the materials.
From a chemical structural point of view it should also be noted that while the approaches listed in section (B) i), ii), and iii) may result in some improvements in the optical stability, these techniques have so far not resulted in the complete suppression of aggregation. On the other hand while an approach such as (B), iv) could be used to obtain materials with good colour stability, the method does require a relatively high processing temperature (˜200° C.) to initiate the crosslinking reaction. In addition, because the reaction involves the formation of very reactive radicals, changes to the polymer backbone are possible which can result in structural defects that are detrimental to the materials' stability and influence other components (e.g., charge-transporting layers).
It is also known that organoboronic acids undergo self-condensation (dehydration) reactions under vacuum or/and heating to form trialkyl-(or triaryl-) boroxine structures.4-6 
Therefore, the use of di- or multi-organoboronic acids, can lead to the formation of cross-linked networks.6 